You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
96 lines
4.5 KiB
HTML
96 lines
4.5 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Asm Labels - Using the GNU Compiler Collection (GCC)</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" title="Using Assembly Language with C">
|
|
<link rel="prev" href="Constraints.html#Constraints" title="Constraints">
|
|
<link rel="next" href="Explicit-Reg-Vars.html#Explicit-Reg-Vars" title="Explicit Reg Vars">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
Copyright (C) 1988-2015 Free Software Foundation, Inc.
|
|
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
|
any later version published by the Free Software Foundation; with the
|
|
Invariant Sections being ``Funding Free Software'', the Front-Cover
|
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
|
(see below). A copy of the license is included in the section entitled
|
|
``GNU Free Documentation License''.
|
|
|
|
(a) The FSF's Front-Cover Text is:
|
|
|
|
A GNU Manual
|
|
|
|
(b) The FSF's Back-Cover Text is:
|
|
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
|
software. Copies published by the Free Software Foundation raise
|
|
funds for GNU development.-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="Asm-Labels"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Explicit-Reg-Vars.html#Explicit-Reg-Vars">Explicit Reg Vars</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Constraints.html#Constraints">Constraints</a>,
|
|
Up: <a rel="up" accesskey="u" href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C">Using Assembly Language with C</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h4 class="subsection">6.43.4 Controlling Names Used in Assembler Code</h4>
|
|
|
|
<p><a name="index-assembler-names-for-identifiers-3489"></a><a name="index-names-used-in-assembler-code-3490"></a><a name="index-identifiers_002c-names-in-assembler-code-3491"></a>
|
|
You can specify the name to be used in the assembler code for a C
|
|
function or variable by writing the <code>asm</code> (or <code>__asm__</code>)
|
|
keyword after the declarator as follows:
|
|
|
|
<pre class="smallexample"> int foo asm ("myfoo") = 2;
|
|
</pre>
|
|
<p class="noindent">This specifies that the name to be used for the variable <code>foo</code> in
|
|
the assembler code should be ‘<samp><span class="samp">myfoo</span></samp>’ rather than the usual
|
|
‘<samp><span class="samp">_foo</span></samp>’.
|
|
|
|
<p>On systems where an underscore is normally prepended to the name of a C
|
|
function or variable, this feature allows you to define names for the
|
|
linker that do not start with an underscore.
|
|
|
|
<p>It does not make sense to use this feature with a non-static local
|
|
variable since such variables do not have assembler names. If you are
|
|
trying to put the variable in a particular register, see <a href="Explicit-Reg-Vars.html#Explicit-Reg-Vars">Explicit Reg Vars</a>. GCC presently accepts such code with a warning, but will
|
|
probably be changed to issue an error, rather than a warning, in the
|
|
future.
|
|
|
|
<p>You cannot use <code>asm</code> in this way in a function <em>definition</em>; but
|
|
you can get the same effect by writing a declaration for the function
|
|
before its definition and putting <code>asm</code> there, like this:
|
|
|
|
<pre class="smallexample"> extern func () asm ("FUNC");
|
|
|
|
func (x, y)
|
|
int x, y;
|
|
/* <span class="roman">...</span> */
|
|
</pre>
|
|
<p>It is up to you to make sure that the assembler names you choose do not
|
|
conflict with any other assembler symbols. Also, you must not use a
|
|
register name; that would produce completely invalid assembler code. GCC
|
|
does not as yet have the ability to store static variables in registers.
|
|
Perhaps that will be added.
|
|
|
|
</body></html>
|
|
|